The story
- Proto-Indo-European*né
- Proto-Indo-European*n̥-
- Proto-Italic*n̥-
- Latinin-
- Middle Englishin-
- Englishin-
- Proto-Indo-European*h₁éǵʰ
- Proto-Indo-European*h₁éǵʰs
- Proto-Italic*eks
- Latinex
- Latinex-
- Proto-Indo-European*dʰeh₁-
- Proto-Indo-European*dʰeh₁k-
- Proto-Indo-European*dʰh₁kyéti
- Proto-Italic*θakjō
- Proto-Italic*fakjō
- Latinfaciō
- Latinefficiō
- Latineffectīvu
- Frencheffectif
- Englisheffective
- Englishineffective
- English todayineffectively
From ineffective + -ly.
Etymology from Wiktionary, CC BY-SA 4.0.